1. Field of the Invention
The present invention relates to a stamping machine, and particularly to a stamping machine used for mounting a retention frame of a heat sink to a motherboard.
2. Description of the Prior Art
Nowadays when a large heat sink is to be attached to a heat generating package such as a Central Processing Unit (CPU), a retention frame is often attached to a motherboard around the CPU in order to provide support for retaining the heat sink. There should be a suitable uniform distance between a bottom face of the retention frame and a top face of the motherboard. If the distance is not uniform, this is known as “floating high.” When floating high exists, it results in non-uniform contact between the heat sink and the CPU, and reduced heat transfer efficiency. The CPU may overheat until it malfunctions or is even damaged beyond repair.
A conventional stamping machine for mounting a retention frame of a heat sink to a motherboard is shown in FIG. 6. The stamping machine 1 comprises a support plane 2 and a stamping arm 4. A recessed receiving portion 3 is formed in a top surface of the support plane 2. The receiving portion 3 is similar to the motherboard (not shown) in shape and size, so that an operator can precisely position the motherboard by inserting it into the receiving portion 3. A stamping assembly 5 comprises a cylinder 6 positioned at a forepart of the stamping arm 4, a stamping block 8 connected to a pair of pistons 7 at a lower end of the cylinder 6, and a support portion 10 disposed in the receiving portion 3. Four stamping posts 9 extend downwardly from four corners of the stamping block 8 respectively. A plurality of cutouts 11 is defined in the support portion 10, corresponding to the stamping posts 9. A plurality of rigid support posts 12 extends upwardly from the support plane 2 in the recess. The support posts 12 are arranged in regular formation around the support portion 10. The stamping block 8 can be driven up and down by the pistons 7 of the cylinder 6.
The stamping machine 1 uses an Alternating Current (AC) of 220V, and the inner control circuit comprises high-voltage components. Referring also to FIG. 7, the control circuit of the stamping machine 1 comprises a first loop, a second loop and a third loop (not labeled). These loops comprise relays K1, K2, touch switches SB1, SB2, SB3 (a touch switch is a switch that is powered on when pressed and is powered off when released), an electromagnetic valve L, and switches k1, k2. The touch switches SB1, SB2 are for controlling the circuit, the touch switch SB3 is for resetting the circuit, the electromagnetic valve L is for controlling the cylinder 6, and the switches k1, k2 are common switches controlled by the relays K1, K2 respectively.
When the touch switch SB1 is pressed to switch on the first loop, the switch k1 is closed under control of the relay K1 to initialize the control circuit. Then, the touch switch SB2 is pressed to switch on the second loop. The switch k2 is closed under control of the relay K2. The electromagnetic valve L controls the cylinder 6 to charge with air, so that the pistons 7 drive the stamping block 8 downwardly. After stamping, the touch switch SB2 is released so that the second loop is switched off. The switch k2 is opened under control of the relay K2, so that the third loop is switched off and the electromagnetic valve L controls the cylinder 6 to discharge with air. The stamping block 8 is then pulled upwardly by the pistons 7.
The motherboard is positioned in the receiving portion 3 of the support plane 2 prior to mounting of the retention frame. The cutouts 11 of the stamping portion 10 are in alignment with through holes (not shown) of the motherboard respectively. When an operating button (not shown) is pressed, the cylinder 6 is charged with air to drive the stamping block 8 downwardly. The stamping posts 9 of the stamping block 8 punch frustum-shaped nails in standoffs of the retention frame, so that the frustum-shaped nails are inserted in the through holes of the motherboard. The retention frame is thereby mounted to the motherboard. Then the operating button is released so that the air in the cylinder 6 is discharged, and the stamping block 8 is retracted to its original position.
However, the stamping machine 1 is liable to cause floating high, as detailed below.
From the aspect of mechanical structure: The conventional stamping machine 1 is typically produced from bakelite. Because bakelite has weak rigidity, it is easily deformed during the stamping process. In addition, the receiving portion 3 of the stamping machine 1 generally conforms to the configuration of the motherboard, so that only one type of motherboard can be fitted into it. If another type of motherboard is to be operated on, the receiving portion 3 needs to be reconfigured accordingly. This increases costs. Furthermore, the stamping posts 9 extending from four corners of the stamping block 8 only act on the standoffs at four corners of the retention frame. Therefore the retention frame is not uniformly pressed onto the motherboard.
From the aspect of air pressure adjustment: The air pressure in the stamping machine 1 cannot be adjusted, therefore the operator cannot ensure that correct pressure is driving the pistons 7. In addition, the operating button must be manually pushed and retained in position to drive the stamping block 8 down, whereupon the operator must release the operating button to return the stamping block 8 to its original position. Such manual operation is subject to human error, and cannot ensure that the retention frame is tightly mounted onto the motherboard. If the retention frame is not tightly mounted, the operator may have to repeat the stamping process several times. This leads to inefficiencies. Furthermore, the rate of stamping of the stamping block 8 cannot be automatically set. This is inconvenient, and can lead to human error on the part of the operator.
From the aspect of circuit control: The stamping machine 1 comprises an Alternating Current (AC) loop. The high-voltage components of the inner control circuit are expensive. In addition, only one button is used in operation. If the bottom is mistakenly pushed, the circuit will be closed immediately and cause an unexpected operation. Furthermore, if an unexpected contingency such as mistaken operation arises, there are no means for quickly and conveniently shutting down the circuit.
In summary, there are a variety of shortcomings in the stamping machine, and difficulties in using the stamping machine. Thus, an improved stamping machine is desired.